Particles with high energy, for example neutrons, protons, alpha radiation and the like (referred to as high-energy particles in the following text), can cause errors in electronic circuits. Some of these errors are referred to as single event upsets (SEU) and single event errors (SEE). When such particles with high energy strike an electronic circuit, they can generate free charge carriers (electrons and/or holes). Said charge carriers can reach critical nodes of the circuit and thus cause errors. Here, critical nodes are nodes whose state and therefore the state of the electronic circuit can be changed by way of such particles with high energy. Examples of such critical nodes are nodes in which a piece of information (for example a bit) is stored. A change in the stored bit value can be caused here by way of the particles with high energy.
In order to avoid such problems caused by free charge carriers, certain rules are used when designing the circuit, such as providing substrate contacts and/or well contacts, via which such free charge carriers can flow away before they reach critical nodes.
However, errors can also occur when such critical nodes are struck directly by particles with high energy. In this case, a state of the node, for example a stored bit value, can also change, wherein, in this case, the measures mentioned above such as substrate contacts or well contacts do not help since the particle or particles strike the critical nodes directly.
In order to solve this problem, multi-bit redundancy is conventionally used together with certain spacing rules. For example, to store a value, three separate memory elements storing the same value can be used. The memory elements are in this case spaced apart from one another in such a way that the probability of a particle with high energy striking two of said three memory elements is kept very low. For this purpose, use is made of the fact that particles with high energy usually move in semiconductor materials such as silicon in a straight line (except for individual scattering events, the probability of which is comparatively low). The spacing of the memory elements is then selected to be greater than the distance that at least the majority of the particles (for example up to a certain energy) in the circuit cover. A distance to be retained can thus be, for example, at least 100 μm, at least 50 μm or at least 20 μm. The selected value also depends here on the degree of reliability intended to be achieved, that is to say how likely a failure may be.
In this way, the probability that two of the three memory elements are struck by a particle is at least greatly reduced.
In the undisturbed case, all three memory elements deliver an identical signal, that is to say an identical stored value. When a memory element is disturbed by a particle with high energy, two of three memory elements still deliver the correct value. The correct value can then be identified by way of a majority decision.
However, with increasing miniaturization of structures, said spacings to be retained can cause problems since, although the structure sizes and therefore the required area for electronic circuits are becoming smaller, the distance that particles in a semiconductor material such as silicon cover can remain the same and therefore the spacing cannot be scaled in the same way. This can lead to the memory elements having to be located in completely different parts of an electronic circuit or could even be located outside of a chip comprising the other components of the electronic circuit. This can at least cause problems in routing.